I LOVE couponing! I haven't spent money on pasta in at least 6 months and yet we eat it several times a week. I also have jars of free pasta sauce, easy mac cups, soup cans, butter, and frozen vegetables among other things. I stocked up on Cheeries for $0.88/box recently, too. Most grocery bills I save at least 50% and all by using printable coupons (I don't get a paper).
As pp stated, Kroger always does unlimited double coupons up to $1 (ie: $0.25 doubles to $0.50, $0.50 doubles to $1, $0.75 doubles to $1). This means you can purchase as many items as you have coupons.
I mainly print my coupons from the internet via blog matchups for a particular store. Those coupons will say "do not double or triple" but Kroger will double them anyway (and if they don't, talk to a manager because it's their policy to double all coupons up to $1). Coupons that you load onto your Kroger card (either from the Kroger website or another) will not double. If you have an identical coupon loaded to your Kroger card in addition to a physical coupon and only buy 1 item, it will take only the electronic one.
Sometimes Remke will do Super Double Coupons. This is when coupons will double up to $2! They don't do it often but expect to go early or find the shelves are pretty bare (and for good reason!).
Meijer also doubles coupons up to $1 but you can only do double coupons up to 2 identical items per transaction. After the first 2 items the coupon comes off at face value. They also have store coupons on their website that can be combined with manufacturer coupons (typically what you'd get in the paper or online). I think they're called Meijer Mealbox coupons. A few other stores (such as Target, Lowes, and sometimes Kroger) will also give out store coupons that can also be combined with manufacturer coupons. I tend not to shop at Meijer (prefer Kroger) unless they have a really good coupon deal, though.
My method is to Google "(store name) matchup (ad start date)" before I go grocery shopping. This will allow me to find blogs that do the work for you. They will tell you how to get the most out of your coupons and most give a final price and whether it's a price you should consider stock-piling on. They will tell you what ad you can find the physical coupon from and/or provide a link to where you can print coupons from the web. Printable coupons can generally be printed 2x/computer (after it prints the first time, hit the back button and then refresh the page; To save paper, flip the first print around and get 2 coupons on the same page). I usually send the links to DH so he can print them, too :). Then, I have my grocery list and put all my coupons into an envelope and off I go!
Sites to get you started:
www.cincysavers.com/blog
http://gracefullysaving.com
http://www.stockpilingmoms.com
Have fun and good luck!